In this investigation, a small amount of antigen will be instilled into segmental bronchus and after 24 or 48 hours, cells and soluble mediators will be sampled from the same segment by bronchoalveolar lavage. Epithelial cells will be obtained by brushing. The same procedure without the antigen will be done in another lab on the opposite side as control. This study will be performed in healthy subjects and in patients with allergic asthma. This study is relevant to the pathogenesis of asthma.